Recently, sucessful attempts in this laboratory to grow and passage the malignant lymphoid colony-forming cell (ML-CFC) from childhood lymphoid cancers have been reported. Techniques have been developed that allow this sub-population of malignant cells with an unlimited growth potential (ML-CFC) to be separated from cell populations with limited growth potentials. Growth of the ML-CFC from bone marrows of children with acute lymphoblastic leukemia and non-Hodgkins lymphoma have enabled initial drug sensitivity patterns to be defined. These exciting results leave significant questions unanswered about the specific growth requirements of the ML-CFCs, and about the in vivo correlation of the chemotherapy sensitivity patterns. Control of the ML-CFC is important since it may result in cure of the patient, for such a correlation has been shown in animal tumor models. An agar assay system has been developed that is reliable and reproducible, but currently ML-CFCs are grown from less that 20% of our patients. The first objective of this grant proposal is to improve this assay system. Growth of the malignant lymphoid colonies has been established in the relative hypoxia (7% oxygen) of a Stulberg chamber. Hypoxia has been shown to be a signficant stimulant of the ML-CFC, but the optimal level of Hypoxia needs to be extablished. Also, the effects of different sera and media need to be defined, for enhanced growth of the NL-CFC has been observed in pilot experiments. The second objective of this proposal is to study drug sensitivity of the ML-CFCs. This assay is ideal for such studies, for both normal myeloid and malignant lymphoid colonies grow side by side under the same conditions. Thus, absolute as well as relative (malignant lymphoid;normal myeloid) drug sensitivity can be calculated. It has been possible to passage (on agar) many of the colonies and, to date, five different cell lines (2 T-cell, 1 B-cell, 2 Null-cell) have been established. Drug sensitivity studies will be done on these cell lines as well as on the primary lymphoid colonies. The drug sensitivity of colony-forming cells on agar has been successful in predicting drug response in animals, but this is a new technique for evaluating childhood lymphoid malignancies.